Using commercially known spindle conveyers of the type mentioned at the outset, in particular vehicle wheels are conveyed through successive treatment stations of a coating plant in which, in a plurality of treatment steps, the vehicle wheels are provided with a surface coating. Known spindle conveyors of the type mentioned at the outset typically take the form of circular conveyors, with the result that all the vehicle wheels always pass through all the treatment stations.
There are vehicle wheels which differ from one another, in that they are to undergo mutually differing treatment steps or have to pass through the treatment stations provided in a coating plant in a different sequence. Conventionally, it has not been possible to treat vehicle wheels which differ in this way in the same coating plant, since it is not readily possible—and only if the construction is redesigned—to adapt the sequence of steps using a circular conveyor.
It is possible to achieve a certain flexibility for example if buffer zones are added to the rail system, for example in that additional secondary rail sections that are connected by way of points units to a main rail section of the circular conveyor are provided. Secondary rail sections of this kind then form a buffer zone in which transport carriages can be parked temporarily.
In the case of commercially known spindle conveyors, each transport carriage carries along a single workpiece spindle, and on their path through the plant the transport carriages always maintain a spacing, which is predetermined by the process sequence or by the dimensions of the vehicle wheels. In particular, the minimum spacing, which is predetermined by the dimensions of the vehicle wheels, is also maintained in a buffer zone. This limits the buffer capacity per meter of rail.
It is an object of the invention to provide a spindle conveyor and a station or plant of the type mentioned at the outset which take account of these ideas.